In England there was a particular problem with a particular pill being used to suicide by overdose. The pill manufacturer switched from selling it by the bottle to selling it in those little individually sealed sheets that are a PITA to open. Suicide rate immediately dropped. Apparently a great many suicides are impulsive and if given a little more time to think about it they will back out.

And yet the UK's suicide rate is about in line with the US's (11.8 per 100,000 vs. 12.0, per Wikipedia), despite the lack of easily-obtainable firearms.